F. TASNÁDI LINKÖPING UNIVERSITY THEORETICAL PHYSICS NEUTRINO OSCILLATIONS & MASS the fundamental discoveries in physics con4nues 1 CONGRATULATIONS - NOBEL PRIZE IN PHYSICS 2016 … the secrets of exotic matter /quantum physics becomes visible in the cold/ David J. Thouless F. Duncan M. Haldane J. Michael Kosterlitz 2 ONE WAY OF DOING FUNDAMENTAL PHYSICS LHC 27 KM STANDARD MODEL Higgs boson the “God particle” 125 GeV 4 July 2012 3 ANOTHER WAY OF DOING FUNDAMENTAL PHYSICS SUSY supersymmetry fermions bosons (super)string theory 4 PARTICLE WORLD - THE STANDARD MODEL /1970 - ???/ neutrinos flavours 5 METAMORPHOSIS IN THE PARTICLE WORLD - NOBEL 2015 “The Nobel Prize in Physics 2015 recognises Takaaki Kajita in Japan and Arthur B. McDonald in Canada, for their key contributions to the experiments which demonstrated that neutrinos change identities (flavours). This metamorphosis requires that neutrinos have mass. The discovery has changed our understanding of the innermost workings of matter and can prove crucial to our view of the universe.” http://www.nobelprize.org Takaaki Kajita Arthur B. McDonald 6 SOURCES OF NEUTRINOS Trillions of neutrinos passing through our bodies every second — almost all of these are produced in fusion reactions in the Sun's core. Solar neutrinos Atmospheric neutrinos Other sources: Big Bang cosmic rays Supernovas … 7 WHAT IS A NEUTRINO? - THE POLTERGEIST “PARTICLE” beta decay: energy conservation: 1929, Niels Bohr: …”possible limitation of the conservation theorems …” 1930: W. Pauli’s letter: “Dear Radioactive Ladies and Gentlemen … there could exist electrically neutral particles, which I will call “neutrons”, that have spin 1/2 and obey the exclusion principle and that further differ from light quanta in that they do not travel with the velocity of light. The mass of the “neutrons” should be of the same order of magnitude as the electron mass and in any event not larger than 0.01 proton mass. ” 8 WHAT IS A NEUTRINO? - THE REAL PARTICLE 1931: The name neutrino by E. Fermi “the Italain little neutral one” 1934: The theory of beta decay by E. Fermi - (anti)neutrinos are included, produced! 1934, Niels Bohr: “… I don’t yet feel fully convinced of the physical existence of the neutrino.” 1956: “Poltergeist is OVER” F. R e i n e s & C. Cowan detect the trace of (anti)neutrino scintillation detector Reines & Cowan 1958: neutrinos are ALWAYS left-handed 9 THE HANDEDNESS - THE VAMPIRE NEUTRINO PARTICLE momentum vs. spinning = handedness p~ p~ ⌫ S~ S~ neutrino mirror 1957, Abdus Salam: “On reflecting a neutrino in a mirror, one sees nothing.” 10 THE MASS - NO AGE OF THE NEUTRINO special relativity: massive particle can NEVER travel at the speed of light left-handed A two-handed vA ⌫¯ MASSLESS NEUTRINO Using massless particles in Dirac’s equations violates left-right symmetry right-handed and results in two ‘components’ equation - neutrino (left) & antineutrino (right). B 11 THE FLAVOURS- THE DIFFERENT NEUTRINOS 1937: the muon or “heavy electron” from cosmic ray 1949: pion, Yukawa’s particle Bruno Pontecorvo in Dubna - investigate the muon decay: µ e− + γ ! µ e− +2⌫ ! conserve the ‘muon-ness’ TWO TYPES OF NEUTRINO ⌫e, ⌫µ n p+e− +¯⌫ ! conserve the ‘electron-ness’ 1975: a new lepton was found: the tau conserve ‘tau-ness’ THREE FLAVOURS OF NEUTRINO ⌫e, ⌫µ, ⌫⌧ 12 WHAT IS A NEUTRINO? - IN THE STANDARD MODEL MASSLESS & LEFT-HANDED “VAMPIRE” standard model NEUTRINO e µ ⌧ | i | i | i electron-flavour muon-flavour tau-flavour 13 MASS EIGENSTATES - SHORT QUANTUM MECHANICS special relativity, energy & momentum conservation: E2 = p2c2 + m2c4 E,p m ! particle particle stays in this mass eigenstate NO OSCILLATION between different m states. | i iφ (t) m e− m | i f | 1i particle spontaneously f , f ARE NOT MASS EIGENSTATES! | 1i | 2i f | 2i It is ‘nonsense’ to speak about the mass if the particle is characterised by fi quantum numbers ! 14 BECAUSE ONLY PARTICLE WITH MASS CAN OSCILLATE /1957, B. Pontecorovo suggests neutrino oscillation/ µ | i neutrino ⌫ spontaneously e , µ ARE NOT MASS EIGENSTATES! | i | i e iφmj (t) e = j λj mj e− | i µ| i iφm (t) e µ = λ mj e− j | i | i P j j | i /coherentP superposition/ Flavour oscillation can happen only if the mass eigenvalues are different! The zero eigenvalue is excluded by the fact that all neutrinos are oscillating. ⌫e = coherent superposition of mass states W− NEUTRINOSe+ HAVE MASS 15 SOLAR (E-)NEUTRINO PROBLEM (1968) - HOMESTAKE EXP. SK: Super Kamiokande deficit of solar neutrinos SNO: Sudbury Neutrino Observatory theoretical rate: 8.5 0.9 SNU ±Standard Solar Model experimental rate: 2.56 0.32 SNU ± SNU: Solar Neutrino Unit 1 SNU = 1 reaction per 1036 target per second) 2 + 8 8 + NEUTRINO OSCILLATION? p+p H+e + ⌫e B Be⇤ +e + ⌫e ! ! 16 EXPENSIVE “DEEP & DARK SCIENCE” IN JAPAN & CANADA SUPER KAMIOKANDE: - operational in 1996 (started 1991) - zinc mine - 1000 m below Earth surface - 50,000 tonnes of pure water (light beam can travel 70 m before intensity is 1/2) - more than 13,000 light detectors to detect Cherenkov radiation - 8B solar neutrinos - muon neutrinos (atmospheric) SUDBURY NEUTRINO OBSERVATORY: - operational in 1999 - 1,000 tonnes heavy-water and for extra shielding ultra-pure water - 9500 light detectors - all flavours of neutrinos (including 8B solar neutrinos) 17 SUPER KAMIOKANDE (SK) KAMIOKA, JAPAN 18 SUDBURY NEUTRINO OBSERVATORY (SNO) CANADA, ONTARIO photo: Lawrence Berkeley Nat'l Lab 19 ICECUBE - ANTARCTICA 20 ICECUBE - THE LABORATORY 21 ATMOSPHERIC NEUTRINOS IN SK - YEAR 1998 ⌫ +e− ⌫ +e− x ! x ISOTROPIC FLUX Φ (⌫ ) long µ 50% Φshort(⌫µ) ⇡ 22 The nobel prize in physics 2015, Popular science background ⌫x +e− ⌫x +e− 2 ! reaction-1: ⌫e + H e− +p+p 2 ! NEUTRINOS IN SNO - YEAR 2001 reaction-2: ⌫x + H ⌫x +p+n ! reaction-1 Φ1(⌫e, Sun) reaction-2 Φ2(all, Sun) Φ2(all, Sun) = Φtheory(⌫e, Sun) 23 The nobel prize in physics 2015, Popular science background NEUTRINO MASS - CONTRADICTIONS! STANDARD MODEL? Contradiction between left-handedness and mass! Solution? 1) right-handed neutrinos are not detected 2) extremely weak weak-interaction Dirac neutrino Majorana neutrino ⌫ =¯⌫ ⌫ =¯⌫ 6 superstring theory (11 dimensions) matter=antimatter mass by Higgs mechanism mass by Higgs mechanism experimentalists theorists supersymmetry (SUSY), string theory, etc… 24 FUNDAMENTAL “PHILOSOPHY” 25 WE NEED THE TECHNOLOGY TO MAKE IT 26 CMS DETECTOR THANK YOU 27 MUON AND TAU NEUTRINOS (SNO WITH SK) reaction-1 3.26 reaction-2 28 THE “AMAZING” NEUTRINOS - PROPERTIES - In our Universe what we see are stars, galaxies, … but what we do not see that the Universe is filled with neutrinos, the second most abundant particles in the Universe after photons; every cm3 of space contains around 300 neutrinos. - Trillions of neutrinos are passing through our bodies every second — almost all of these are produced in fusion reactions in the Sun's core - interact only with the weak force. λ 1.7 1017 m 106 d(Sun-Earth) H2O ⇡ ⇥ ⇡ ⇥ 16 λPb 1.5 10 m ⇡ ⇥ mp 5 105 m m - Direct mass measurements: “massless”? ⇥ ⌫e ⇡ e ⇡ 1840 - Indirect mass measurements: m⌫ > 0 29.